"They" could always make it harder to transfer money from inside the US system to the "outside" world. This is what an exit-tax is, basically making it harder for established people to move away from the system. Or AML for international wires. Or Minimum Corporate Tax.

Unluckily for First-World countries, the politicians seems to be focused on the symptoms rather than the disease itself. This will not change course of what will happen, of course.